1. Field of the Invention
The present invention relates to a digital image processor such as a digital printer and a data processing thereof.
2. Description of the Prior Art
In a digital printer or the like, digital image data are read by an image reader section, modified by an image processor section according to the print characteristics and edited according to the editing mode specified with an operational panel. After the data processing, the image is printed on a paper by a printer section.
In the image reader section, a digital image of a document is read at a specified resolution. Therefore, the information on the document which exceeds the resolution is lost inevitably when the image is read. In the printer section, the image data can not be reproduced with perfect fidelity. Therefore, an image printed on the paper is reproduced by the printer, the information is lost inevitably to a certain degree and the quality of the image regenerated by the printer is degraded.
The degradation of image may not be a large problem when the image is reproduced from the original document. However, when the image is reproduced again from the hard copy, the quality of the image may be degraded to a large degree. Some printers use an outline font. However, even if an image is reproduced with fidelity with use of outline font, the quality of the hard copy of the reproduced image is degraded, especially as to the contour.
There is no problem if the copying is performed from the digital source in a floppy disk or the like. However, a hard copy (analog image) is reproduced again in many cases as to the compatibility or the convenience. Therefore, it is desired to improve the quality of a hard copy.
In U.S. Pat. No. 4,847,641, a contour line of an image is improved by estimating the original pattern or by using smoothing. However, this method cannot restore the deformed contours which occurred on reading and on printing.
An object of the present invention is to provide an image processor which does not degrade an image when it is reproduced from a hard copy.
Another object of the present invention is to provide an image processor which can add additive information to the original image data for restoring contours when the image is reproduced.
In one aspect of an image processor according to the present invention, additive information on the contour of an image is generated and embedded in the reproduced image in a hard copy. For example, characteristic points of a density or a color different from that of the image are added inside a contour of the image. When a hard copy including the additive information is reproduced, the additive information is extracted from received image data on the hard copy, and the contour of the image is restored from the additive information extracted from the received data. Preferably, the additive information is embedded again for the next generation of the reproduced image.
In another aspect of the present invention, image regions including no additive information on contour are distinguished, and additive information is generated for the image regions without additive information. On the other hand, for the image regions including additive information, the additive information is extracted and an image is restored on basis only of the additive information. Then, the image data in the restored image regions and those of the non-restored image regions are synthesized and sent for reproduction.
In a third aspect of the present invention, a read error is detected, in a comparison of the restored data with the received image data, when the difference of the comparison is larger than a predetermined value. In case of a read error, the received image data is corrected by generating additive information on contour for the region wherein the read error occurs. If necessary, the read correction can be prohibited.
An advantage of the present invention is that contours of an image lost in a hard copy can be restored as far as the additive information can be extracted from the hard copy.
Another advantage of the present invention is that the image quality is not degraded if the reproduced hard copy is reproduced repeatedly.
A third advantage of the present invention is that even for a document such as a patched image including image regions without additive information on contour, the as-received image data on the image regions are synthesized with the image data of the other image regions restored from the additive information.
A fourth advantage of the present invention is that the image quality of a half-tone image is not degraded in a reproduced hard copy.
A fifth advantage of the present invention is that a read error can be detected and corrected for an image including additive information on contour.